California Climate Change Glossary

Letter M

MAGICC. Climate model that calculates average atmospheric temperatures and sea levels. It is used by IPCC for the construction of the SRES scenarios. (Lenn)

Marginal Cost. The cost on one additional unit of effort. In terms of reducing emissions, it represents the cost of reducing emissions by one more unit. (IPCC)

Marginal Cost Pricing. The pricing of commercial goods and services such that the price equals the additional cost that arises from the expansion of production by one additional unit. (IPCC)

Marine Biosphere. A collective term for all living marine organisms. (IPCC)

Market Barriers. Conditions that prevent or impede the diffusion of cost-effective technologies or practices that could mitigate GHG emissions. (IPCC)

Market Damages. The value of damages generated by climate change (or some other environmental change) and evaluated based on information available to and usable by a competitive market. (IPCC)

Market Penetration. The share of a given market that is provided by a particular good or service at any given time. (IPCC)

Market Potential (or Currently Realizable Potential). The portion of the economic potential for GHG emissions reductions or energy-efficiency improvements that could be achieved under existing market conditions, assuming no new policies and measures. (IPCC).

Market-based Incentives. Measures intended to directly change relative prices of energy services and overcome market barriers. (IPCC)

Mauna Loa. A volcano on the island of Hawaii where scientists have maintained the longest continuous collection of reliable daily atmospheric records. (EPA)

Mean Seal Level (MSL). The average Relative Sea Level over a period, such as a month or a year, long enough to average out transients such as waves. (Lenn)

Measures. Actions that can be taken by a government or group of governments, often in conjunction with the private sector, to accelerate the use of technologies or other practices that reduce GHG emissions. (EPA)

Medieval Warm Period. Term introduced by the British meteorologist Hubert Lamb in 1965, for a period between the 9th and 13th century during which it was extremely warm on many locations in and around Europe. Wine was grown in Scandinavia and agriculture was possible on Greenland. This was determined by studying snow lines in the mountains and temperatures in deep boreholes and has given us the impression that temperature changes may have occurred before. Geochemist Wallace Broecker thinks that cyclic processes in the oceans cause a warmer period once in every 1500 years. (Lenn)

Megaton (Mt). One million (10⁶) tons. Greenhouse gas emissions are often measured in megatons. (Australia)

Meteorology. The science of weather-related phenomena. (EPA)

Methane (CH4). A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 24.5. Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and oil, coal production , and incomplete fossil fuel combustion. The atmospheric concentration of methane has been shown to be increasing at a rate of about 0.6% per year and the concentration of about 1.7 parts per million by volume (ppmv) is more than twice its preindustrial value. However, the rate of increase of methane in the atmosphere may be stabilizing. (EPA)

Metric Ton. Common international measurement for the quantity of greenhouse gas emissions. A metric ton is equal to 2,205 lbs or 1.1 short tons. (EPA)

Million Metric Tons - MMT. Common international measurement for million metric tons of carbon dioxide equivalents (MMT CO2) to describe the magnitude of greenhouse gas (GHG) emissions or reductions. See PDF file of some representations of 1 MMT of CO2 in familiar equivalents. (CARB)

Mitigation. A human intervention to reduce the sources or enhance the sinks of substances that pollute the environment, for example greenhouse gases. (Lenn)

Mole Fraction. The ratio of the moles of one component of a system to the total moles of all components present. Typical values for long-lived greenhouse gases are in the order of mmol/mol (parts per million: ppm) or nmol/mol (parts per billion: ppb). Mole fraction differs from volume mixing ratio, often expressed in ppmv. (Lenn)

Montreal Protocol. Protocol on substances that deplete the ozone layer, signed in Montreal in 1987. It controls the consumption and production of chlorine- and bromine-containing chemicals that destroy stratospheric ozone, such as CFCs, methyl chloroform, carbon tetrachloride, and many others. (Lenn)

Mount Pinatubo. A volcano in the Philippine Islands that erupted in 1991. The eruption of Mount Pinatubo ejected enough particulate and sulfate aerosol matter into the atmosphere to block some of the incoming solar radiation from reaching Earth's atmosphere. This effectively cooled the planet from 1992 to 1994, masking the warming that had been occurring for most of the 1980s and 1990s. (EPA)